There have been broadly employed radiation images such as X-ray images for diagnosis of the conditions of patients in medical practice. Specifically, radiation images using an intensifying-screen/film system, which have achieved enhancement of speed and image quality, are still used on the scene of medical treatment as a conventional imaging system having high reliability and superior cost performance in combination.
However, these image data are so-called analog image data, in which free image processing or instantaneous image transfer cannot be realized.
Recently, there appeared digital system radiation image detection apparatuses, as typified by a computed radiography (also denoted simply as CR) and a flat panel radiation detector (also denoted simply as FPD).
Systems for use in a digital radiation image detector include a direct system and an indirect system.
There is known, for example, a radiation image detector using a solid-state imaging sensor (such as CCD or CMOS), as a direct system, which is used in non-destructive testing for industrial use or is inserted into a mouth to collect stationary pictures for use in dental radiography.
An indirect system uses a phosphor layer (scintillator layer) containing a phosphor, in which X-rays are initially converted to visible radiation and the visible radiation is converted to a signal charge through a photoelectric conversion substrate provided with photoelectric conversion elements such as a photodiode, CCD or CMOS and introduced to a capacitor for charge accumulation.
There is broadly used an indirect system which is simple and exhibits higher sensitivity, compared to a direct system.
There are also known radiation image detectors used in an indirect system, such as a radiation image detector of a system in which a phosphor layer is provided directly on a planar light-receiving element, and a radiation image detector of a system in which a phosphor layer provided on the substrate of a scintillator panel is bonded to photoelectric conversion elements which are two-dimensionally disposed on a photoelectric substrate.
In such a radiation image detector of a bonding system, uniformity of contact of a phosphor layer with photoelectric conversion elements greatly affects image quality.
Accordingly, to reduce bubbles produced between the phosphor layer and the photoelectric conversion elements, for example, there is known a production method, wherein a photoelectric conversion substrate is coated with a transparent adhesive and is pasted onto a scintillator panel under reduced pressure, and then, the transparent adhesive is hardened under atmospheric pressure (as described in, for example, Patent document 1).
However, a non-uniformed image is sometimes produced in such a radiation image detector obtained by the foregoing production method, so that there has been desired a radiation image detector in which occurrence of image unevenness is reduced.